Hummer H1 (2006+). Manual - part 54

OBD-60

On-Board Diagnostics

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DTC P0087 Fuel Rail Pressure Too Low (Figure OBD-19)

Figure OBD-19:   Fuel Pressure Regulator and Fuel Pressure Sensor Circuits

Circuit Description

The engine control module (ECM) monitors fuel rail pressure (FRP) using the FRP sensor. If the sensor indicates a pressure less
than the commanded rail pressure plus a possible transitional overshoot, the ECM will set DTC P0087 for fuel rail pressure too
low.

Conditions for Setting the DTC

The actual FRP is less than 0.0 MPa at 0-400 RPM. OR The actual FRP is less than 22.5 MPa at more than 600 RPM.

Action Taken When the DTC Sets 

• The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails. 

• The control module records the operating conditions at the time the diagnostic fails. The control module stores this informa-

tion in the Freeze Frame/Failure Records. 

• The ECM will limit fuel injection. 

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 On-Board Diagnostics  OBD-61

5745804

Conditions for Clearing the MIL/DTC 

• The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic 

runs and does not fail. 

• A current DTC, Last Test Failed, clears when the diagnostic runs and passes. 

• A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related 

diagnostic.

• Clear the MIL and the DTC with a scan tool. 

Diagnostic Aids 

• A restricted fuel supply line may cause DTCs P0087 and P1093 to set at the same time. When ambient temperatures are be-

low 0°C (32°F), the fuel tank pickup screen may be iced over from water in the fuel tank. 

• If power enhancing devices have been attached to the fuel rail pressure sensor circuits, this DTC may set and adversely ef-

fect the fuel system components.

Step

Action

Value(s)

Yes

No

    1

NOTE: Before clearing DTC(s) use the scan tool “Capture info” to
record Freeze Frame and Failure Records for reference, as data will be
lost when “Clear Info” function is used 

Was the “On-Board Diagnostic (OBD) System Check” performed?

Go to step 2.

Go to OBD 

System

Check.

    2

If any of the following DTCs are set, go to that DTC first.

 P0168 

 P0090 

Are any of these DTCs set?

Go to the 

Diagnostic

for each 

Trouble Code 

in numerical 

order

Go to Step 3 

    3

Attempt to start the engine.

Does the engine start and idle?

Go to Step 4 

Go to Engine 

Cranks but 

Does Not 

Run

    4

1.

Observe the Freeze Frame/Failure Records for this DTC.

2.

Turn OFF the ignition for 30 seconds.

3.

Start the engine.

4.

Operate the vehicle within the Conditions for Running the DTC. 
You may also operate the vehicle within the conditions that you 
observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

Go to Step 5 

Intermittent 

Go to Diag-

nostic Aids

    5

1.

Turn ON the ignition, with the engine OFF.

2.

Observe the Actual Fuel Rail Pressure parameter with a scan tool.

Is the Actual Fuel Rail Pressure Parameter within the specified range?

1-1.8

MPa

Go to Step 6 

Go to Step 10 

    6

Inspect the engine oil for fuel contamination. 

Did you find and correct the condition?

Go to Step 17

Go to Step 7

OBD-62

On-Board Diagnostics

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    7

1.

Install the J 44638 Vacuum Gage on the fuel fitting located on the 
right side front of the engine.

2.

Start and run the engine at idle.

3.

Observe the vacuum gage while increasing RPM slowly to wide 
open throttle (WOT) in Park or Neutral.

Does the vacuum measure less than the specified value through the en-
tire RPM range?

5 in

Go to Step 8 

Go to Step 11

    8

1.

Start and idle the engine until the idle speed drops to 680 RPM.

2.

Command the fuel pressure control to 160 MPa with a scan tool.

3.

Observe the Actual Fuel Rail Pressure parameter with a scan tool.

Is the Actual Fuel Rail Pressure parameter more than the specified
value?

145

MPa

Go to Step 9

Go to Fuel 

System Diag-

nosis - High 

Pressure Side 

    9

NOTE: If the fuel temperature is near 121°C (250°F) during the dupli-
cation of the complaint, or in the Failure Records for this DTC, inspect
for a restriction in the fuel cooler air flow or the fuel heater always ON.

Operate the vehicle within the conditions for which the customer com-
plaint occurs.

Does the vacuum measure less than the specified value through the en-
tire operating range?

12 in

Go to Diag-

nostic Aids

Go to Step 11 

   10

1.

Disconnect the fuel rail pressure sensor. 

2.

Observe the Actual Fuel Rail Pressure with a scan tool.

Does the Actual Fuel Rail Pressure measure more than the specified
value?

175

MPa

Go to Step 15

Go to Step 14

   11

Replace the fuel filter. 

Did you compete the replacement?

Go to Step 12 

   12

1.

Ensure that the J 44638 is still installed on the engine.

2.

Start and run the engine under the conditions for which the high 
vacuum occurred.

Does the vacuum measure less than or equal to the specified value?

5 in at 

idle or 

12 in at 

high

speed

Go to Step 17

Go to Step 13

   13

Repair the restriction in the fuel supply lines between the fuel tank and
the fuel injection pump. 

Did you complete the repair?

Go to Step 17 

   14

Test the fuel rail pressure sensor signal circuit 509 (YL) for a short to
ground.

Did you find and correct the condition?

Go to Step 17

Go to Step 16

   15

Replace the faulty fuel rail pressure sensor. 

Did you complete the replacement?

Go to Step 17

   16

Replace the faulty engine control module (ECM). 

Did you complete the replacement?

Go to Step 17

Step

Action

Value(s)

Yes

No

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 On-Board Diagnostics  OBD-63

5745804

   17

1.

Clear the DTCs with a scan tool. 

2.

Turn OFF the ignition for 30 seconds.

3.

Start the engine.

4.

Perform the turbocharger learn procedure. 

5.

Operate the vehicle within the Conditions for Running the DTC. 
You may also operate the vehicle within the conditions that you 
observed from the Freeze Frame/Failure Records. 

Did the DTC fail this ignition?

Go to Step 2

Go to Step 18

   18

1.

Using the Scan Tool select “Capture Info,” Review Info.” Are any 
DTC’s displayed that have not been diagnosed?

Go to the 

applicable

DTC table.

System OK.

Step

Action

Value(s)

Yes

No